Over twenty-five years ago, a method of using a pulse signal to actuate a valve was introduced to control the flow rate and fluid pressure of liquids through a spray nozzle. Since then, this technique has remained largely the same or unused because it results in spotty spray patterns due to long dead times. The actuator for the valve cannot respond fast enough even if the frequency of the pulse signal is increased; the fluid leaks, which creates problems such as in an agricultural setting (e.g. crops, plants, trees, vegetables, winery), where sprayers are used to apply prescribed amounts of nutrients, herbicides, insecticides and water. In manufacturing settings, sprayers are used to apply coatings of paint colors and layers of chemicals, and ink on surfaces such as plastic, paper, semiconductors, metals, and so on. In food industries, spray nozzles clean equipment and surfaces.
When pulse signals have been used to control the spray of fluids, the ejection of fluid from conventional single nozzles has been controlled by a single pulse stream. The voltage polarity of the pulse signal is arbitrarily selected so that when the pulse is at a high value, then liquid is dispersed by the nozzle, and when the pulse is at a low value, no liquid is dispersed. The ON state is arbitrarily chosen to refer to when liquid is propelled or ejected, and the OFF state to no liquid. The duration of the ON or OFF pulse can be varied (PWM, pulse width modulated) to generate to vary the flow rate.